The goal of this proposed research is to test the concept that the metabolism of rods and cones follows a daily rhythm, and that the rhythms of rods and cones are displaced in time by 12 hours. Recent work has shown that the two classes of visual cells shed membranes from their outer segments preferentially at a certain time of day--the rods, early in the morning; the cones, early in the night. Five experiments are described which will explore the possibility that other aspects of visual cell metabolism similarly show daily rhythms. The experiments involve analysis by electron microscopy or autoradiography of events which are localized in one or the other of the four major subdivisions of the visual cells: outer segment, inner segment, nucleus, and synaptic body. The factors which will be examined are membrane-shedding, protein synthesis, RNA synthesis, autophagy, and synaptic morphology, each of which will be assessed by quantitative methods.